Elastic, ephemeral in-line deduplication service

ABSTRACT

A deduplication service can be provided to a storage domain from a services framework that expands and contracts to both meet service demand and to conform to resource management of a compute domain. The deduplication service maintains a fingerprint database and reference count data in compute domain resources, but persists these into the storage domain for use in the case of a failure or interruption of the deduplication service in the compute domain. The deduplication service responds to service requests from the storage domain with indications of paths in a user namespace and whether or not a piece of data had a fingerprint match in the fingerprint database. The indication of a match guides the storage domain to either store the piece of data into the storage backend or to reference another piece of data. The deduplication service uses the fingerprints to define paths for corresponding pieces of data.

RELATED APPLICATIONS

This application claims priority to and is a continuation of U.S. patentapplication Ser. No. 16/807,636, titled “AN ELASTIC, EPHEMERAL IN-LINEDEDUPLICATION SERVICE” and filed on Mar. 3, 2020, which claims priorityto and is a continuation of U.S. Pat. No. 10,621,151, titled “ANELASTIC, EPHEMERAL IN-LINE DEDUPLICATION SERVICE” and filed on Sep. 25,2015, which are incorporated herein by reference.

BACKGROUND

The disclosure generally relates to the field of data processing, andmore particularly to data processing for storage efficiency.

An enterprise level data center or storage system can be logicallyseparated into a storage front end and a storage backend. The storagefront end includes devices that are exposed to clients of the storagesystem. The storage front end devices may be referred to as storagecontrollers, servers, or filers. The storage backend includes devicesthat host data and serve data to the storage front end. The storagebackend devices may be referred to as storage arrays, storage devices,attached storage, or networked storage.

An organization with a storage system configured for archival or coldstorage purposes will have high storage density (e.g., shingled magneticrecording (SMR) devices) in the storage backend and have minimalcomputational resources (e.g., low cost processors and a relativelysmall amount of memory) in the storage front end. The minimalcomputational resources will often be devoted to reliability and spacemanagement. An archival or cold storage system is often designed withminimizing cost per gigabyte (GB) as the primary goal. Such a system canbe characterized with write-and-read-rarely patterns. Thus, the systemis not configured for maximizing input/output operations per second(IOPS).

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure may be better understood by referencingthe accompanying drawings.

FIG. 1 depicts different instances of a deduplication redirectorrequesting deduplication of files.

FIG. 2 depicts deduplication service responses to the deduplicationrequests from the deduplication redirector instances.

FIG. 3 depicts delete of a file that has been deduplicated by thededuplication service.

FIG. 4 is a flowchart of example operations for processing storagerequests in an environment that uses distributed in-line deduplicationservice.

FIG. 5 is a flowchart of example operations for generating a response toa deduplication service request.

FIG. 6 depicts a flowchart of example operations for processing adeduplication service response.

FIG. 7 depicts a flowchart of example operations for processing anupdate request and requesting a deduplication service for the updaterequest.

FIG. 8 depicts a flowchart of example operations for incrementingreference count data for the deduplication service.

FIG. 9 depicts a flowchart of example operations for decrementingreference counts of a deduplication service.

FIG. 10 depicts an example deployment of the deduplication service andthe fingerprint database of the deduplication service.

FIG. 11 depicts an example computer system with a distributeddeduplication service module.

DESCRIPTION

The description that follows includes example systems, methods,techniques, and program flows that embody aspects of the disclosure.However, it is understood that this disclosure may be practiced withoutthese specific details. For instance, this disclosure refers primarilyto an external, elastic, ephemeral deduplication service alone, but thedisclosed deduplication service may be provided as one of many servicesin a services framework that adapts to service demand from a storagedomain and resource management in a compute domain. In other instances,well-known instruction instances, protocols, structures and techniqueshave not been shown in detail in order not to obfuscate the description.

Overview

An environment (e.g., an organization's data center) can be logicallyseparated into a storage domain and a compute domain. The storage domainincludes devices and software of a storage front end and a storagebackend. The compute domain includes other devices and software that arenot part of the storage domain. For instance, the compute domain caninclude a server farm or compute cluster. The compute domain may be aheterogeneous compute domain (e.g., servers in a computer cluster couldhave varying amounts of random access memory (RAM), could have flash orhard disk drive (HDD) storage, etc.). The two domains can share networkresources (e.g., switches, routers, cabling, etc.) and have dedicatednetwork resources. This separation of the compute domain and the storagedomain allows for managing resources in the domains independently andconfiguration of the domains for particular purposes. For instance, thestorage domain can be configured with resources that support a primarypurpose of the storage domain, such as cold storage or archiving. Thus,the storage domain can be configured with high density storage devices(e.g., tape storage and SMR devices) and low computational resources(e.g., slower processors with smaller caches and less system memory).With less performance oriented resources in the storage domain, thestorage domain may not be capable of efficiently performing variousservices (e.g., deduplication, compression, encryption, watermarking,etc.). In some cases, the storage domain can perform services (e.g.,deduplication), but not without violating service level objectives(SLOs). This disclosure refers to an in-line deduplication service thatis external to the storage domain, elastic, and ephemeral. The servicecan be considered elastic because it can expand or contract based onavailable resources and service demand. The service can be consideredephemeral because the underlying resources (e.g., processors, memory,etc.) can fail or disappear without warning.

With more computational resources in the compute domain, an in-linededuplication service can be provided to the storage domain. The in-linededuplication is provided to the storage domain while being de-coupledfrom the storage domain. The in-line deduplication service can utilizecomputational resources of the compute domain and provide service to thestorage domain without violating SLOs defined for either domain. Sincethe compute domain possibly takes priority over the storage domain, thecompute domain may take resource management actions that reduceresources available to the deduplication service. Thus, thededuplication service is designed to gracefully react to diminishingresources in the compute domain. However, the compute domain mayprovision additional resources for the deduplication service. Therefore,the deduplication service is also configured to scale up and takeadvantage of additional resources. In addition to the compute domainresources, the deduplication service uses resources of the storagedomain for failover. The deduplication service maintains a fingerprintdatabase and reference count data in compute domain resources, butpersists these into the storage domain for use in the case of a failureor interruption of the deduplication service in the compute domain. Anamespace is defined in the storage domain for the deduplication serviceto maintain this failover data. The deduplication service responds toservice requests from the storage domain with indications of paths in auser namespace and whether or not a piece of data had a fingerprintmatch in the fingerprint database. The indication of a match guides thestorage domain to either store the piece of data into the storagebackend or to reference another piece of data. The deduplication serviceuses the fingerprints to define paths for corresponding pieces of data.Using the fingerprints as paths supports idempotent writes that avoidinconsistencies that could arise during concurrent writes of the samedata or when the deduplication service is interrupted.

Example Illustrations

FIGS. 1-3 are diagrams depicting example operations of an in-linededuplication service that provides deduplication to a storage domain ofa system. The diagrams depict an example of deduplicating a file beingwritten into a storage backend, writing a file into the storage backend,and deletion of a file in the storage backend. FIGS. 1-3 are annotatedwith a series of numbers. These numbers represent occurrences ofoperations. An annotation with a number and letter (e.g., 1A and 1B)indicates operations that occur concurrently in the exampleillustration. Although these operations are ordered for this example,the ordering is one example to aid in understanding this disclosure andshould not be used to limit the claims. Subject matter falling withinthe scope of the claims can vary with respect to the order and some ofthe operations.

FIG. 1 depicts different instances of a deduplication redirectorrequesting deduplication of files. In FIG. 1 , an environment includeshardware and software that can be logically and physically separatedinto a storage domain and a compute domain. The storage domain includesa deduplication redirector instance 103, a deduplication redirectorinstance 105, and a storage backend 125. The deduplication redirectorinstances 103, 105 run in storage front end devices (not depicted) ofthe storage domain. Deduplication redirector instances are deployedthroughout the storage front end to be in the path of the input/outputof the storage backend 125. In this example, the deduplicationredirector instances 103, 105 break down a file into ordered file datachunks (“chunking files”), and request deduplication of the file datachunks. The storage backend 125 has defined within it a user space 127and a service space 129. The user space 127 is a namespace and/orportion of the storage backend that is accessible to clients (e.g.,applications) that submit storage requests to the storage front end. Theservice space 129 is a namespace and/or portion of the storage backendthat is used by a deduplication service 111 residing in the computedomain. Although used by the deduplication service 111, the servicespace 129 can be accessed via the storage domain front end devices ordirectly from compute domain devices that host components of thededuplication service.

In this illustration, the service space 129 includes file data chunksand the user space 127 includes file manifests. In this description, afile manifest is a file that identifies file data chunks that constitutea file. The file manifest is used to reconstruct a file with the filedata chunks. The service space 129 includes file data chunks “C1”, “C2”,“C3”, and “C4”. The user space 127 includes two file manifests. A filemanifest for a file “C” is depicted and indicates “*C1”, “*C2”, and“*C4.” The annotation of a “*” is used to represent a path to the filedata chunk in the service space 129. Thus, the file manifest for file“C” has path values that can be used to obtain the file data chunks C1,C2, and C4. The second file manifest is for a file “A.” The filemanifest for file A indicates “*C2” and “*C3.” Thus, the file datachunks can be obtained with the indicated paths and used to constructthe file A. File data chunk C2 has already been deduplicated and isshared by files A and C.

The deduplication service 111 in the compute domain includes multiplecomponents to provide deduplication to the storage domain. Thededuplication service includes three deduplicator instances 113, 115,117. The deduplicator instances 113, 115, 117 can be deployed ondifferent machines and/or virtual machines in the compute domain. Thededuplication service 111 can scale up by deploying additionaldeduplicator instances or scale down by terminating deduplicatorinstances. The elasticity of the deduplication service 111 is evidencedby its ability to scale up or down in response to demand by the storagedomain and/or to comply with resource management in the compute domain.The deduplication service 111 can also reassign deduplication tasksamong deployed instances in the case of failures or resource managementactions. Deduplicator instances use a fingerprint database 119 in theirassociated storage resources to determine whether a deduplication can beperformed. For this example, the fingerprint database 119 is maintainedin storage resources associated with the deduplicator instances 113,115, and 117. For example, the fingerprint database 119 can be in flashstorage devices in the compute domain associated with compute resourcesthat host the deduplicator instances 113, 115, and 117. The fingerprintdatabase 119 can also be in a storage resource of the compute domainthat is accessible to any compute domain resource. Another component ofthe deduplication service 111 is a garbage collector 121. The garbagecollector 121 maintains reference count data for donor file data chunks(i.e., the file data chunks referenced for deduplication). The garbagecollector 121 also manages donor file data chunks stored in the servicespace 129 in accordance with the reference count data 123.

At 1A, the deduplication redirector instance 103 receives a request towrite a file “D” into the storage backend 125. At 1B, the deduplicationredirector instance 105 receives a request to write a file “X” into thestorage backend 125. These requests from clients are first processed bya communication/network layer before flowing into or being interceptedby the deduplication redirector instances 103, 105. For this example, itis assumed that deduplication is to be requested for these files.However, deduplication redirector instances 103, 105 may evaluate therequests against policies to determine whether the deduplication serviceshould be requested for these files.

At 2A, the deduplication redirector instance 103 communicates with aservice dispatcher 101 to determine a deduplicator instance(s) toprovide the deduplication service. At 2B, the deduplication redirectorinstance 105 communicates with the service dispatcher 101 to determine adeduplicator instance(s) to provide the deduplication service. Theservice dispatcher 101 is a component running in the compute domain. Theservice dispatcher 101 may determine provisioning and assignment ofother services, but this disclosure focuses on determining deduplicatorinstances to provide deduplication services to the storage domain. Theservice dispatcher 101 communicates location (e.g., network address andport) of at least one deduplicator instance to the deduplicationredirector instance 103 and at least one deduplicator instance to thededuplication redirector instance 105. The location information can becached by the redirector instances to avoid repeated lookups from theservice dispatcher 101 for subsequent deduplication requests. Theservice dispatcher 101 can be contacted off the request path to refreshthe cached location information. There can be cases when thededuplication service is not available (e.g., insufficient resources inthe compute domain for deduplication). In these cases, the servicedispatcher 101 will notify deduplication redirector instances that thededuplication service is unavailable.

At 3A, the deduplication redirector instance 103 chunks the file “D”into file data chunks “D1” and “D2.” At 3B, the deduplication redirectorinstance 105 chunks the file “X” into file data chunks “X1” and “X2.”Fragmenting files into file data chunks can be in accordance with aconfigured size. The configured size may be a size based on theunderlying storage technology (e.g., filesystem data block size) oradministrator defined size (e.g., maximum configured size for an objectin object storage), as examples. The configured size may also bedynamic. For instance, the chunk size can be defined to vary dependingupon performance goals (e.g., service level objectives) and/orperformance metrics (e.g., network latency). As examples, chunk size maybe a function of network latency and IOPS at a storage front end deviceperforming the chunking.

At 4A, the deduplication redirector instance 103 supplies the file datachunks “D1” and “D2” to the deduplicator instance(s) of the deduplicatorinstances 113, 115, 117 identified by the service dispatcher 101. At 4B,the deduplication redirector instance 105 supplies the file data chunks“X1” and “X2” to the deduplicator instance(s) of the deduplicatorinstances 113, 115, 117 identified by the service dispatcher 101. Anyone of the deduplicator instances 113, 115, 117 may have been launchedin response to the communication between the service dispatcher 101 andeither of the deduplication redirector instances 103, 105.

At 5, the deduplicator instances 113, 115 generate fingerprints from thereceived file data chunks and determine whether the generatedfingerprints have matches in the fingerprint database 119. For thisillustration, the service dispatcher 101 previously identified thededuplicator instance 113 to the deduplication redirector instance 103and the deduplicator instance 115 to the deduplication redirectorinstance 105. So, the deduplicator instance 117 is not involved in theillustration, although the deduplicator instance 117 may be busy withother deduplication requests. Furthermore, alignment of a deduplicatorinstance per deduplication redirector instance is only a side effect ofthis simple illustration. The service dispatcher 101 may assign multiplededuplicator instances to process different sets of file data chunksfrom a deduplication redirector instance. In addition, the servicedispatcher 101 may assign file data chunks from different deduplicationredirector instances to a same deduplicator instance, perhaps due toresource policies or resource management in the compute domain.

FIG. 2 depicts deduplication service responses to the deduplicationrequests from the deduplication redirector instances. The exampleoperations depicted in FIG. 2 illustrate example results of thededuplication requests of FIG. 1 .

At 1A, the deduplication service 111 returns a response for the filedata chunks “D1” and “D2.” The deduplicator instance 113 determined, atstage 5 of FIG. 1 , that a fingerprint for D1 matched a fingerprint forC1 (“#D1==#C1”). The fingerprint for C1 was already in the fingerprintdatabase 119. The deduplicator instance 113 indicates in the response tothe deduplication redirector instance 103 that D1 had a fingerprintmatch and indicates the path to the donor file data chunk C1. Thededuplicator instance 113 determined that there was no match in thefingerprint database 119 for the fingerprint generated from D2. Withouta match in the fingerprint database 119, the deduplicator instance 113determined a path deterministically derived from the fingerprint of D2and inserts the D2 fingerprint (“#D2”) into the fingerprint database119. The path is deterministically derived from the D2 fingerprint toensure consistency in the case of service disruptions or failures thatlead to a file data chunk being written more than once into the servicespace. This also relies on the storage backend supporting idempotentwrites to a same path. The response to the deduplicator instance 113 forD2 indicates the path derived from the D2 fingerprint, and that D2 didnot have a fingerprint match.

At 1B, the deduplication service 111 returns a response for the filedata chunks “X1” and “X2.” The deduplicator instance 115 determined thata fingerprint for X2 matched a fingerprint for C2 (“#X2==#C2”) that wasin the fingerprint database 119. The deduplicator instance 115 indicatesin the response to the deduplication redirector instance 105 that X2 hada fingerprint match and indicates the path to the donor file data chunkC2. The deduplicator instance 115 determined that there was no match inthe fingerprint database 119 for the fingerprint generated from X1.Without a match in the fingerprint database 119, the deduplicatorinstance 115 determined a path deterministically derived from thefingerprint of X1 and inserts the X1 fingerprint (“#X1”) in thefingerprint database 119. The response to the deduplicator instance 115for X1 indicates the path derived from the X1 fingerprint, and that X1did not have a fingerprint match.

At 2A, the deduplication redirector instance 103 stores the file datachunk D2 based on the deduplication response. Since the deduplicationresponse indicates that D2 did not have a fingerprint match, then thededuplication redirector instance 103 stores (via a storage backendinterface or subsystem) D2 to the path *D2 in service space 129. D2 isnow available as a donor file data chunk. Since D1 had a fingerprintmatch, D1 is deduplicated. In other words, D1, which is redundant inlight of C1, is not stored into the storage backend user space 127.

At 2B, the deduplication redirector instance 105 stores the file datachunk X1 based on the deduplication response for X1. Since thededuplication response indicates that X1 did not have a fingerprintmatch, then the deduplication redirector instance 105 stores (via astorage backend interface or subsystem) X1 to the path *X1 in theservice space 129. X1 is now available as a donor file data chunk. SinceX2 had a fingerprint match, X2 is deduplicated.

After storing the file data chunks that lacked a matching fingerprint inthe fingerprint database 119, the deduplication redirector instances103, 105 store file manifests into the user space 127. At 3A, thededuplication redirector instance 103 stores a file manifest for thefile D into the user space 127. The file manifest for file D indicatespaths in order of the corresponding file data chunks to reconstruct thefile D. The paths indicated in the file manifest are *C1 and *D2. At 3B,the deduplication redirector instance 105 stores a file manifest for thefile X into the user space 127. The file manifest for file X indicatesordered paths to file data chunks to reconstruct the file X. The pathsindicated in the file manifest for X are *X1 and *C2.

At 4 and 5, the deduplication service 111 persists deduplication statedata (i.e., the fingerprint database 119 and the reference count data123) into the storage backend. The deduplication service 111 persiststhe fingerprint database 119 into the storage backend 125 as afingerprint database 219. “Persisting” the fingerprint database 119 intothe storage backend refers to the operation(s) performed to maintain acurrent fingerprint database in a durable storage space. This allows fora recovery of the fingerprint database if a failure or resourcemanagement action occurs in the compute domain that impacts availabilityof the fingerprint database 119. As previously mentioned, the in-linededuplication service is supported with ephemeral resources that can“disappear” because of a failure, interruption, or reallocation.Persisting the fingerprint database 119 into persistent storage allowsthe in-line deduplication service to tolerate this ephemeral nature ofthe supporting resources. As examples, the deduplication service 111 canpersist the fingerprint database 119 by employing a backup applicationwith snapshot functionality, logging database updates in a persistentstorage in the compute domain, etc. The fingerprint database 219 may notbe the same as the fingerprint database 119 due to a service failure orinterruption that does not allow for graceful termination of thededuplication service. Frequency of persist operations can be configuredin accordance with a storage domain policy. Persist operations can beconfigured with longer time gaps between persist operations, whichincreases the batching of updates. This maximizes the sequentialbandwidth utilization of the storage domain, which may be the goal of astorage domain policy defined for an archival storage system. Thespecific length of the time gap between persisting operations takes intoaccount the client tolerance of lost changes to the fingerprint database119. Thus, the bandwidth utilization of the storage domain is weighedagainst the performance impact due to overwriting a file data chunk dueto its fingerprint not persisting to the fingerprint database 219.Similar to the fingerprint database 119, the deduplication service 111persists the reference count data 123 into the storage backend 125 asreference count data 223.

FIG. 3 depicts delete of a file that has been deduplicated by thededuplication service. At some point, a client may request that a filebe deleted. In FIG. 3 , a client requests deletion of file “A” at 1. At2, the deduplication redirector instance 103 determines that file A hasbeen deduplicated since the user space 127 has a file manifest for thefile A. Since the file A has been deduplicated, the deduplicationredirector instance 103 moves the file A manifest into a service spacefor files to be deleted, referred to herein as delete space 301.Afterwards, the garbage collector 121 of the deduplication service 111is triggered to maintain the delete space 301 and reference count data123. At 3, the garbage collector 121 examines content of the deletespace 301. The garbage collector 121 determines that the delete space301 includes the file A manifest. At 4, the garbage collector 121decrements references counters for C2 and C3 in the reference count data123 in response to discovering the file A manifest in the delete space301. For this illustration, decrementing the reference counter for C3results in 0 references to C3. Therefore, the garbage collector 121removes the C3 fingerprint from the fingerprint database 119 at 5. Thegarbage collector 121 also deletes C3 and the path *C3 from the servicespace 129.

The following flowcharts depicted in FIGS. 4-9 describe exampleoperations for a distributed in-line deduplicaton service. Theillustrations of FIGS. 1-3 referred to files, file data chunks, and afile manifest. But the storage domain is not limited to a filesystemstorage technology. For instance, the storage backend interface may bean object storage interface. In light of the different storagetechnologies (e.g., block based storage, file based storage, objectbased storage) and overloading of terms across technologies (e.g., theterm object), the flowcharts refer to a data unit, data sub-units, anddata manifest to avoid confusion among terms and unintended confinementto a particular technology due to term use.

FIG. 4 is a flowchart of example operations for processing storagerequests in an environment that uses distributed in-line deduplicationservice. FIG. 4 refers to a redirector performing the operations. Aredirector is a generic label used for executing program code thatintercepts, receives, or detects a storage request after communicationlayer processing and that is a component of an in-line deduplicationservice, but deployed into a storage front end.

At block 401, a redirector receives a storage request with indication ofa data unit. The redirector runs on a storage front end device. Forexample, the redirector may intercept a request that indicates a filehandle or an object key. The storage request may be in accordance with aweb service protocol that has already passed through transmissioncontrol protocol/Internet protocol processing, for example. Or, thestorage request may be in accordance with a network attached storage orstorage area network based protocol.

At block 403, the redirector determines the type of request. Theredirector can determine the type of request from metadata of a request.Although different protocols can define a variety of different requests,most requests can be categorized as a write request, read request, or adelete request. Therefore, the example operations address thesecategories of requests.

If the received request is a write type of request, then the requestreferences or includes the indicated data unit. The redirector extractsthe data unit from the request or obtains the data unit from thereference in the request. The redirector then divides the data unit(previously referred to as chunking when dividing a file) into datasub-units in accordance with a sub-unit size at block 421. Theredirector determines sub-unit size from configuration information. Asdiscussed previously, the sub-unit size can be based on the storagesystem configuration and/or adapt to performance goals. Dividing thedata unit can involve the redirector storing each of the data sub-unitsin a buffer or memory designated for data units with correspondingunfulfilled deduplication requests (“in-flight deduplication requests”).The redirector can store the individual data sub-units with indicationsof the data unit and order of the data sub-units. Dividing can involvethe redirector creating a copy of the data unit and modifying the copyof the data unit to mark the beginning of each sub-unit, thus leveragingthe order already provided by the data unit. The redirector could alsomodify the data unit to include dividing markers without making a copyof the data unit.

At block 423, the redirector determines a deduplicator instance(s) basedon the number of yielded sub-units. A deduplication service policyprovided to the redirector from the services framework may specify amaximum amount of data to be processed by a single deduplicatorinstance. Based on this threshold and the size of the sub-units, theredirector can request a number of deduplicator instances that conformsto the policy. Instead of the redirector requesting a certain number ofdeduplicator instances, the redirector may submit a deduplicationservice request that includes an indication of the size of the data unitand/or a number of sub-units. A deduplication service can then determinea number of deduplicator instances to assign to the service request. Inaddition, the deduplication service may select particular deduplicatorinstances based on capability when deduplicator instances haveheterogeneous resources.

At block 425, the redirector creates a data unit manifest for the dataunit. The redirector creates the data unit manifest to indicate the datasub-units that constitute the data unit and order of the data sub-unitsfor data unit reconstruction. This data unit manifest is later populatedwith paths to the constituent sub-units. Although a path can be a paththrough a hierarchical namespace (e.g., directories to traverse), a pathcan also be a key in a flat namespace (e.g., namespace in object basedstorage). Whether a flat namespace or a hierarchical namespace, the pathcan be considered a namespace identifier that is used to obtain data.

At block 427, the redirector requests deduplication for the datasub-units by the deduplicator instance(s) determined at block 423. Theredirector creates a number of requests and sends the requests to theinterfaces or locations for the deduplicator instance(s) identified bythe deduplication service. The deduplication service may present asingle interface to the storage front end. In that case, the redirectorsends the requests to the single interface, and the deduplicationservice forwards the request(s) to the corresponding deduplicatorinstance(s). The redirector can send a single request that includes thedata sub-units, a request for different sets of the data sub-units, or arequest for each data sub-unit. In addition to the data sub-units, therequest(s) identifies the corresponding data unit for proper associationof deduplication responses. Since the deduplicator instance isstateless, the deduplicator instance uses the data unit identifier thatis eventually returned in a deduplication response to determine anappropriate data unit manifest.

If the redirector determined at block 403 that the request was readrequest, then the redirector determines whether the indicated data unitis a data unit manifest in user space at block 407. The redirector mayobtain the indicated data unit (e.g., obtain an object by object key orfile by file handle) and examine the obtained data unit to determinewhether it is a data unit manifest. This can be determined from theretrieved data being a listing of paths to data sub-units or themetadata having a value that indicates a data unit manifest.

If the redirector determines that the obtained data unit is a data unitmanifest, then the redirector constructs the data unit according to themanifest at block 409. The redirector issues read requests via thestorage backend interface for the data sub-units in accordance with thepaths indicated in the data unit manifest. The paths are to datasub-units in service space in the storage backend. The redirector or anassociated process can then construct the retrieved data sub-units inaccordance with the sub-unit order indicated in the data unit manifest.

At block 411, the redirector returns the constructed data unit to therequestor indicated in the request. For instance, the redirector passesthe constructed data unit back to a network layer that processed theoriginal request.

If the redirector determined that the data unit obtained from user spacewas not a data unit manifest, then the redirector returns the obtaineddata unit back to the requestor at block 413. For instance, theredirector forwards the response from the storage backend interface to anetwork layer.

If the redirector determined that the request was a delete request atblock 403, then the redirector determines whether the indicated dataunit is a data unit manifest at block 415. Similar to block 407, theredirector may obtain the indicated data unit (e.g., obtain an object byobject key or file by file handle) and examine the obtained data unit todetermine whether it is a data unit manifest. Depending upon theunderlying storage technology and/or organization of data units and dataunit metadata, the redirector may request metadata for the indicateddata unit instead of obtaining the indicated data unit from user space.With the metadata, the redirector can determine whether the metadataindicates that the data unit in user space is a data unit manifestwithout fetching the data unit.

If the data unit in user space is a data unit manifest, then theredirector moves the data unit manifest to a delete path in servicespace at block 419. The delete path is inspected by the garbagecollector for maintaining a correct reference count.

If the data unit in user space is not a data unit manifest, then theredirector forwards the delete request of the indicated data unit viathe storage backend interface at block 417.

FIG. 5 is a flowchart of example operations for generating a response toa deduplication service request. FIG. 5 refers to a deduplicatorinstance as performing the example operations. A deduplicator instancerefers to an executing instance of program code that performsdeduplication operations.

At block 501, a deduplicator instance receives a deduplication requestfor a data sub-unit. The deduplication request includes the datasub-unit and indicates a data unit. The indication of the data unit is avalue or identifier that travels with the deduplication request andresponse to allow the redirector to resolve a response back to anindication of the data unit.

At block 503, the deduplicator instance generates a fingerprint of thedata sub-unit. For instance, the deduplicator instance generates afingerprint with a cryptographic hash function (e.g., a Secure HashAlgorithm (SHA) or MD5) or Rabin's fingerprinting algorithm.

At block 505, the deduplicator instance determines whether the generatedfingerprint is already in a fingerprint database.

If the generated fingerprint is already in the fingerprint database,then the deduplicator instance determines a path that is associated withthe matching fingerprint in the fingerprint database at block 513. Eachrecord or entry in the fingerprint database includes a fingerprint and apath deterministically derived from the fingerprint.

At block 515, the deduplicator instance generates a deduplicationresponse. The generated deduplication response indicates the path andindicates that the fingerprint of the sub-unit matched a fingerprint inthe fingerprint in the database. This indication of the matchingfingerprint signals to the redirector that the data sub-unit is not tobe stored into the storage backend because it would be redundant.

If there is no matching fingerprint in the fingerprint database at block505, then the deduplicator instance generates a path in service space atblock 507. The deduplicator instance generates the pathdeterministically from the fingerprint as previously mentioned. Forinstance, the deduplicator instance can use a text or numericrepresentation of the fingerprint itself as the path.

After generating the fingerprint and corresponding path, thededuplicator instance inserts them into the fingerprint database atblock 509. Presence of the fingerprint in the fingerprint databaseallows for the data sub-unit to be a donor for another sub-unit.

At block 511, the deduplicator instance generates a deduplicationresponse. The generated deduplication response indicates the path andindicates that the fingerprint of the sub-unit did not have a match inthe fingerprint in the database. This indication of absence of amatching fingerprint signals to the redirector that the data sub-unit isto be stored into the storage backend at the indicated path.

At block 517, the deduplicator instance sends the generateddeduplication response (generated either at block 515 or block 511).

FIG. 6 depicts a flowchart of example operations for processing adeduplication service response. FIG. 6 refers again to the redirector asthe entity performing the example operations for consistency with FIG. 4.

At block 601, a redirector receives a deduplication response from adeduplicator instance. The deduplication response indicates a datasub-unit and a path. The deduplication response indicates the datasub-unit as it was indicated in the deduplication request. For example,the data sub-unit can be indicated with a data unit identifier (e.g.,file handle or file name) and an identifier corresponding to the datasub-unit identifier (e.g., offset). The path is a path in service spacegenerated from the data sub-unit fingerprint. For example, the path maybe “/deduplication/#D1/” with #D1 being a string representation of theD1 fingerprint.

At block 603, the redirector determines a data unit manifestcorresponding to the data unit for the data sub-unit. When theredirector created the deduplication service request, the redirectorcreated a data unit manifest for the data unit and initialized the dataunit manifest with indications of the data sub-units. The redirectorstored the data unit manifest in a memory associated with the storagefront end device that hosts the redirector. The data unit manifests areidentified based on the corresponding data unit. This allows theredirector to look up or access the data unit manifest with a data unitidentifier. After determining the data unit manifest, the redirectorupdates the data unit manifest to indicate the path from thededuplication service response. The redirector locates a field or entryin the data unit manifest for the data sub-unit indicated in thededuplication service response and overwrites or modifies the field orentry to indicate the path.

At block 605, the redirector determines whether the deduplicationservice response indicates that the data sub-unit had a fingerprintmatch. The deduplication service response includes a flag or value thatindicates the lack of a match in the fingerprint database. Without afingerprint match, the indicated data sub-unit cannot be deduplicated.

At block 607, the redirector stores the data sub-unit to the pathindicated in the deduplication service response if the deduplicationservice response indicates that the data sub-unit did not have afingerprint match. The redirector generates a command or request that ispassed to the storage backend interface. The command or request causesthe data sub-unit to be stored at the indicated path. The redirector maygenerate a separate command or request for creation of the path in theservice depending upon the underlying storage technology. Control flowsfrom block 607 to block 609.

At block 609, the redirector determines whether the data unit manifestindicates a path for all data sub-units. This determination is madeeither after the redirector determines that the deduplication serviceresponse indicates that the data sub-unit had a fingerprint match orafter the redirector stores the data sub-unit that did not have afingerprint match into the storage backend. The redirector can make thisdetermination with different techniques based on structure of the dataunit manifest. The redirector can scan the data unit manifest todetermine whether all of the indicated data sub-units have pathsindicated. The redirector can maintain a count of data sub-units forwhich a deduplication service response has been received and compare thecount against a total number of data sub-units of the data unit todetermine whether a data unit manifest is complete. If the data unitmanifest is complete, then control flows to block 611. Otherwise,control flows to block 613.

At block 611, the redirector stores the data unit manifest into thestorage backend. The redirector generates a command that is passed tothe storage backend interface to cause the data unit manifest to bestored into the storage backend into the user space. If the request fromthe client indicated a path, then the data unit manifest is stored intothe user space at the indicated path. The data unit manifest isidentified as the data unit in user space. For instance, the data unitmanifest is identified as file ‘A’ if the client request was for a file‘A’.

At block 613, the redirector determines whether another deduplicationservice response is received. The redirector can check a queue or bufferused for deduplication service responses. Alternatively, an interruptmechanism can be used to invoke the redirector when a deduplicationservice response is received at the host storage front end device.

FIG. 5 processed requests that were either a read, write, or delete typeof request. As mentioned previously, a request may more accurately becategorized as an update request than a write request for some storageprotocols. FIG. 7 depicts a flowchart of example operations forprocessing an update request and requesting a deduplication service forthe update request. FIG. 7 again refers to the redirector as performingthe example operations for consistency with FIG. 5 .

At block 701, a redirector determines whether a data unit indicated inan update request is a data unit manifest. The redirector can obtain thedata unit from the user space with an identifier in the update requestand examine the data unit to determine whether it is a data unitmanifest. The redirector may be able to retrieve metadata of the dataunit without retrieving the entire data unit to determine whether themetadata indicates the data unit in user space is a data unit manifest.If the indicated data unit is a data unit manifest, then control flowsto block 705. Otherwise, control flows to block 703.

At block 703, the redirector passes the update request to the storagebackend interface or allows the update request to continue flowing tothe storage backend interface. The redirector may call a function thatinvokes the storage backend interface and passes along the updaterequest. The redirector may return or move the update request to abuffer, queue, or memory location that the storage backend interfaceconsumes.

At block 707, the redirector determines a data sub-unit(s) impacted bythe update request. The redirector can compare offsets of the datasub-units indicated in the data unit manifest against the offset(s)indicated in the update request to determine impacted sub-units.

At block 709, the redirector divides the update data into data sub-unitsand indicates size and order of the update data sub-units. Theredirector divides the update data in accordance with the division ofdata sub-units indicated in the data unit manifest. If the data unit isoperated upon in fixed size sub-units, then the update data units willalign with the sub-units. However, the storage redirector may reconcileupdate extents, for example, with the data sub-units. The redirectorwill modify the update data to align with the data sub-units. Forexample, a 27 KB object may have been divided into 10 KB sub-units. Theobject may have a first sub-unit starting at 0, a second sub-unitstarting at 10, and a third sub-unit starting at 20. Assume update datathat is 12 KB in length with an offset of 5 KB. For this illustration,the update data impacts the first 2 sub-units. The redirector wouldretrieve the first two sub-units according to their paths in the dataunit manifest. The redirector would then create a first update datasub-unit with 5 KB from the first data sub-unit starting at 0 of thedata unit, and with the first 5 KB of data from the update data. Theredirector would then create a second update data sub-unit with theremaining 7 KB of the update data and the last 3 KB of data from thesecond data sub-unit. The redirector then records information thatindicates the paths for the first two sub-units may be modified. Forexample, the redirector can set a flag in the data unit manifest foreach of the impacted data sub-units. In addition, the redirector can setthe flag in an in-memory data structure created from the data unitmanifest. As an example, the redirector can create a hash table indexedby data unit identifier to each of the data sub-units.

At block 711, the redirector determines a deduplication(s) instance toprovide the deduplication service. The redirector communicates with aservice dispatcher to determine the deduplicator instance(s) that canprovide a deduplication service for the update data.

At block 713, the redirector indicates a mapping between the updatesub-unit(s) and the impacted data sub-unit(s). The redirector canindicate the mapping by associating an update request identifier (e.g.,a session identifier or message hash extracted from the header of theupdate request) with the update sub-unit. In some cases, the redirectorcan avoid an explicit indication of mapping when the update sub-unit(s)aligns with the data sub-unit(s) (e.g., correspondence of offsets).

At block 715, the redirector requests deduplication for the updatesub-unit(s). The redirector sends the update sub-unit(s) to thededuplicator instance(s) identified by the service dispatcher.

With data deduplication, reference counts are often maintained. Thereference counts indicate the number of references to donor data. Thiscount is used ensure donor data with existing references are notdeleted. As discussed earlier, the deduplication service includes agarbage collection component that maintains the reference counts. Thegarbage collection component performs various operations for the in-linededuplication service to tolerate the ephemeral nature of the supportingresources. FIGS. 8 and 9 depict example operations for maintainingreference count data of a deduplication service. FIG. 8 depicts aflowchart of example operations for incrementing reference count datafor the deduplication service. FIGS. 8 and 9 refer to a garbagecollector performing the example operations.

At block 801, the garbage collector detects a count trigger. A counttrigger can be startup of the garbage collector and/or the deduplicationservice. The garbage collector may startup initially, after a failure,after an interruption, or after a management action driven termination.The count trigger can also be elapse of a defined periodic interval, anumber of writes detected by the deduplication service, resourcemanagement actions in the compute domain, etc.

At block 803, the garbage collector determines a user space in a storagebackend to scan. The garbage collector can be exposed by configurationto a particular user space. The configuration information can specify apath, mount point, etc.

At block 805, the garbage collector quiesces operations that target theuser space. To avoid changes that impact the reference count, thegarbage collector requests the storage backend to quiesce operationsthat target the user space to be scanned.

At block 807, the garbage collector creates a checkpoint for the userspace after the user space has stabilized from the quiesce request. Forinstance, the garbage collector scans the user space based oncheckpoints to limit the scan to updates made to the user space sincethe previous scan. This leverages copy-on-write employed by the storagebackend.

At block 809, the garbage collector determines any data unit manifestsadded to the user space since the last checkpoint. For each new dataunit the garbage collector discovers in the user space during thecheckpoint scan, the garbage collector evaluates the data unit ormetadata of the data unit to determine whether the data unit is a dataunit manifest.

At block 811, the garbage collector begins selecting each discovereddata unit manifest. At block 813, the garbage collector begins selectingeach data sub-unit indication in the selected data unit manifest.

At block 815, the garbage collector increments a reference count for thedata sub-unit indicated by the selected data sub-unit indication. Thedata unit manifest indicates a path for each data sub-unit, and eachpath can be used to find the corresponding data sub-unit. So, the pathcan also be used to index reference counts. Thus, the garbage collectorcan determine a path for a data sub-unit from the data unit manifest,and access a reference count data structure with the path as an index.The access yields the reference count, which the garbage collector thenincrements.

At block 817, the garbage collect determines whether there is anadditional data sub-unit indicated in the data unit manifest. If so,then control flows back to block 813 for selection of the next datasub-unit indication in the selected data unit manifest. Otherwise,control flows to block 819.

At block 819, the garbage collector determines whether there is anadditional discovered data unit manifest. If so, then the garbagecollector proceeds to select the next data unit manifest at block 811.If all data unit manifests of the checkpoint being scanned have beenprocessed, then control flows to block 821.

At block 821, the garbage collector unquiesces the operations targetingthe user space. The garbage collector notifies the storage backend thatI/O targeting the user space and/or mount point can be unblocked.

FIG. 9 depicts a flowchart of example operations for decrementingreference counts of a deduplication service. In addition to maintainingthe reference counts, the garbage collector also deletes data unitmanifests that have been moved for deletion.

At block 901, the garbage collector detects a removal trigger. A removaltrigger corresponds to one or more conditions for decrementing referencecounts. Examples of a removal trigger include expiration of a timeinterval, detecting performance of a number of delete requests in thestorage domain, detecting a threshold number of data unit manifests in apath defined for data unit manifests to be deleted (“delete path”), aresource related threshold (e.g., consumed storage space or memoryexceeding a threshold), etc. The garbage collector can periodicallymonitor the delete path and begin decrement and cleanup operations whena threshold number of data unit manifests are discovered in the deletepath.

At block 903, the garbage collector determines whether the delete pathis empty. The delete path is a path in the deduplication servicenamespace specified for data unit manifests to be deleted. If the deletepath is empty, then the garbage collector waits until a next removaltrigger at block 905. Otherwise, control flows to block 907.

At block 907, the garbage collector quiesces operations that target theuser space corresponding to the service space. To avoid changes thatimpact the reference count, the garbage collector requests the storagebackend to quiesce operations that target the user space. Although thegarbage collector is not scanning the user space when performing removaloperations, the garbage collector may remove a data sub-unit with areference count of 0 concurrently with a new data sub-unit beingdeduplicated with the data sub-unit that has been removed. A servicespace may correspond to more than one user space (e.g., multiple userspaces and a service space correspond to a same mount point or domain).In that case, the garbage collector performs removal operationsseparately for each user space.

At block 909, the garbage collector begins selecting each data unitmanifest in the delete path. At block 911, the garbage collector beginsselecting each data sub-unit indication in the selected data unitmanifest.

At block 913, the garbage collector decrements a reference count for thedata sub-unit indicated by the selected data sub-unit indication. Thegarbage collector can determine a path for a data sub-unit from the dataunit manifest, and access a reference count data structure with the pathas an index. The access yields the reference count, which the garbagecollector then decrements.

At block 915, the garbage collect determines whether there is anadditional data sub-unit indicated in the data unit manifest. If so,then control flows back to block 911 for selection of the next datasub-unit indication in the selected data unit manifest. Otherwise,control flows to block 917.

At block 917, the garbage collector determines whether there is anadditional data unit manifest in the delete path. If so, then thegarbage collector proceeds to select the next data unit manifest atblock 909. If all data unit manifests in the delete path have beenprocessed, then control flows to block 919.

At block 919, the garbage collector clears the delete path and removeseach data sub-unit with a 0 reference count after requesting removal ofthe corresponding fingerprints from the fingerprint database. Afterprocessing the data unit manifests in the delete path, the garbagecollector cleans up data sub-units that are no longer referenced. Thiscleanup includes requesting removal of fingerprints from the fingerprintdatabase and removing the data sub-units. As the garbage collectordecrements reference counts, the garbage collector can track those datasub-units by fingerprint, for example, when the reference count isdecremented to 0 and generate the requests for removal (deletion or markfor deletion) the fingerprint from the fingerprint database. The garbagecollector would submit the removal request to a deduplicator instance ora process/node responsible for maintaining the fingerprint database. Thegarbage collector could also scan the reference count data to determineall data sub-units with a 0 reference count after processing the dataunit manifests in the delete path. With the fingerprints of datasub-units having a 0 reference count, the garbage collector can requestremoval of the fingerprints from the fingerprint database and delete thedata sub-units from the paths corresponding to the fingerprints. Thegarbage collector also deletes the data unit manifests in the deletepath after processing them.

At block 921, the garbage collector unquiesces the operations targetingthe user space. The garbage collector notifies the storage backend thatI/O targeting the user space and/or mount point can be unblocked.

The above illustrations have referred to the storage domain and computedomain, but deployment of the deduplication service within a computedomain can vary. For instance, each deduplicator instance can be runningon a separate physical device, on virtual machines, or mixed deploymentof individual devices and virtual machines. In addition, the softwarecomponents can be organized differently than in the exampleillustrations. The deduplication tasks, for instance, can be furtherdecomposed than suggested in the example illustrations above. As anexample, the deduplication service can instantiate program code forfingerprint generation separately from program code for accessing andmaintain the fingerprint database. These different software componentscan communicate with each other within the compute domain (e.g., usinginter-process communication mechanisms).

FIG. 10 depicts an example deployment of the deduplication service andthe fingerprint database of the deduplication service. In FIG. 10 , anenvironment includes a storage domain and a compute domain 1015. Thestorage domain includes a storage front end 1001 and a storage backend1013. The storage front end 1001 is depicted with two storage front enddevices, although it likely includes a greater number. Each storagefront end device hosts an operating system that includes at least aredirector. One of the depicted storage front end devices is illustratedas hosting an operating system 1011. The operating system 1011 includesa software stack. The software stack includes a network module 1005, adeduplication redirector 1007, and a backend storage interface 1009. Thenetwork module 1005, which itself may be a network stack, processesclient requests in accordance with the encapsulating communicationprotocol. Output of the network module 1005 is received or interceptedby the deduplication redirector 1007. Output that is not modified by thededuplication redirector 1007 flows to the backend storage interface1009 for servicing of the client request. As described above, thededuplication redirector 1007 may itself generate requests based on theclient request and pass those requests to the storage backend interface1009. The storage backend 1013 includes a number of storage devices,arrays, disk racks, etc.

The storage domain and the compute domain 1015 are interconnected with anetwork 1002, which can include a variety of communication hardware thatcan vary by consuming domain. For instance, a subnet of the network 1002can communicate in accordance with Fibre Channel while the rest of thenetwork communicates in accordance with Ethernet.

The compute domain 1015 includes several physical compute devices andcorresponding resources. The compute domain can include its own storagedevices (e.g., solid state storage devices). The compute domain 1015supports a services framework or services architecture 1017. Theservices framework 1017 provides services to the storage domain inaccordance with resources provisioned to the services framework 1017from the compute domain, and some resources from the storage domain. Theservices framework 1017 can provide several services, but only anexternal, elastic, ephemeral deduplication service 1023 is illustrated.The services framework 1017 includes a service dispatcher 1019 and aservice manager 1021. The service dispatcher 1019 determines instancesof services for the storage domain. The service manager 1021 managesresources in accordance with a defined resource policy and/or resourcemanagement actions driven by a resource manager (e.g., clusterscheduler) of the compute domain 1015, and manages resources allocatedto the services framework 1017 among the different services. Theservices framework 1017 is considered elastic because it expands andcontracts in accordance with service demand, available resources, andperformance goals. This expansion and contraction can involve transferof service instances among nodes (virtual machines or physical machines)in the compute domain 1015, instantiating new service instances,terminating service instances.

The deduplication service 1023 includes three deduplicator instances(1025, 1027, 1029), a fingerprint database 1039, a garbage collector1041, and a reference count database 1043. The deduplicator instances1025, 1027 run on a virtual machine 1031 of the compute domain. Thededuplicator instance 1029 runs on its own physical device (andassociated resources) of the compute domain 1015. The garbage collector1041 can also run on a virtual machine, or its own physical device. Thegarbage collector 1041 can be a process, for example a backgroundprocess, managed by the service manager 1021. The service manager 1021can determine when the garbage collector 1041 is run. The servicemanager 1021 can explicitly invoke the garbage collector 1041 or defineconfiguration information that influences running of the garbagecollector 1041. The fingerprint database 1039 is depicted in thisexample illustration as a scale out database distributed across nodes1033, 1035, 1037. The nodes 1033, 1035, 1037 can be virtual machinenodes, physical device nodes, or a combination thereof. Implementing thefingerprint database as a distributed scale out database allows thefingerprint database to expand or contract in accordance with resourcechanges in the services framework 1017 and/or changes in service demandpressure from the storage domain. The nodes can be responsible fordifferent shards of the fingerprint database in the case of horizontaldatabase partitioning. As a more specific example, the fingerprintdatabase 1039 can be implemented as a distributed hash table with thefingerprints as the indexes or keys. The services framework 1017 can addnodes to the fingerprint database 1039 to scale up and remove nodes toscale down. With the distributed database, each node's data of thefingerprint database can be persisted to storage separately. Thedatabase can also be configured with a built-in data redundancy policy,for example replication or erasure coding, to avoid recovering from apersisted database when a node fails. If nodes fail, then new nodes canbe rapidly instantiated from any redundant copies of the database, ifavailable, on the compute domain or started with the persisted data inthe storage domain. If an individual node fails, then a new node can beinstantiated or started with the persisted data of the failed node.

A failure of one of the nodes that maintain the fingerprint database ora failure of a deduplicator instance would be considered a partialfailure of the deduplication service. A partial failure due to loss of adeduplicator instance can impact throughput performance for ingestingdata, but can be remedied by launching another deduplicator instance,assuming sufficient resources are available. A partial failure of thededuplication service related to the fingerprint database, for examplethe loss of a database node, may result in loss of some fingerprints.When a fingerprint is lost, deduplicator instances do not have awarenessof whether the corresponding data has already been stored. If thecorresponding data is received again, a receiving deduplicator instanceprocesses the corresponding data as new to the deduplication service.Thus, the deduplicator instance will generate a fingerprint to beinserted into the fingerprint database. The corresponding data will bewritten into storage (again). Since the destination is deterministicallyderived from the fingerprint, the data will be written to the samelocation (i.e., the already stored data is overwritten with the samedata). Despite the impact on efficiency by a partial failure, thededuplication service and storage continue to be operational.

In some situations, the deduplication service may become unavailable.This would be considered a total failure of the deduplication service.When this occurs, storage continues to operate without deduplication.Although storage efficiency is impacted, the storage system remainsoperational.

Variations

The flowcharts are provided to aid in understanding the illustrationsand are not to be used to limit scope of the claims. The flowchartsdepict example operations that can vary within the scope of the claims.Additional operations may be performed; fewer operations may beperformed; the operations may be performed in parallel; and theoperations may be performed in a different order. For example, theoperations depicted in FIG. 4 can vary when dividing data units ishandled within the deduplication service (e.g., by a deduplicatorinstance) instead of the redirector. The redirector would send adeduplication service request with the data unit, and a deduplicatorinstance can divide the data unit into data sub-units before fingerprintgeneration. In addition, the redirector may determine the deduplicatorinstance(s) (block 423) prior to dividing the data unit into datasub-units (block 421). In some embodiments, the identified deduplicatorinstances influence how the data unit is divided by the redirector. Asanother example of how operations can vary from those depicted, theredirector may evaluate a received request against a service policy.This evaluation would guide the redirector in requesting (or notrequesting) the deduplication service. It will be understood that eachblock of the flowchart illustrations and/or block diagrams, andcombinations of blocks in the flowchart illustrations and/or blockdiagrams, can be implemented by program code. The program code may beprovided to a processor of a general purpose computer, special purposecomputer, or other programmable machine or apparatus.

Another possible variation relates to data that is maintained for thededuplication service. The example illustrations discuss maintain thedata sub-unit paths in the fingerprint database. But this can be avoidedsince the paths are deterministically determined from the fingerprints.The fingerprint itself may be the path or the path can be inexpensivelyreconstructed from the fingerprint (e.g., concatenating a value with thefingerprint). Avoiding storing the path in addition to the fingerprintreduces the metadata footprint of the deduplication service.

Example illustrations related to maintenance operation (e.g., operationsby the garbage collector) refer to quiescing. However, it is notnecessary to quiesce operations that target the user space whenperforming maintenance operations. The storage system may implement aparadigm that allows for maintenance operations to run on a space whilealso servicing requests that target the space. For example, the storagesystem may implement fine grain locking on objects accessed by thegarbage collector. As another example, the storage system may implementa pre-determined/static data partitioning paradigm.

The above example illustrations refer to accessing data in a certainmanner that presumes a particular type of data structure, but the claimsshould not be limited to a particular data structure. For instance, theexample illustrations refer to accessing the reference count data withthe fingerprint as an index, but embodiments are not limited to encodingthe reference count data in an indexed structure. The reference countdata can be stored in a database that uses the paths as keys, or acombination of data unit identifier and data sub-unit identifier (e.g.,the key can be a file handle and offset). With respect to the data unitmanifest, the entries in the manifest can be inodes that indicate thepaths to the data sub-units.

Furthermore, the example illustrations align sub-units to fixed sizes.Embodiments, however, are not limited to fixed size data sub-units. Dataunits can be divided into variable sized data sub-units and thefingerprints in the fingerprint database can be for variable sized datasub-units. For update requests in a system that allows for variablesized data sub-units, the redirector can avoid maintaining a mappingbetween update sub-units and impacted sub-units. This mapping can alsobe avoided if the system implements copy-on-write since a different dataunit manifest would be created in response to an update to a data unit.For the copy-on-write scenario, the system would rename the data unitmanifest as it would rename any other data unit in accordance with thecopy-on-write mechanism.

The examples refer to software components including a “deduplicationredirector,” “redirector,” and a “manager.” These constructs are used togenerally refer to implementation of functionality for variousoperations in the deduplication service and the services framework thatis external to the storage domain. These constructs are utilized sincenumerous implementations are possible. A redirector or a manager may bea program, application, thread, process, implemented on a particularcomponent or components of a machine (e.g., a particular circuit cardenclosed in a housing with other circuit cards/boards), implemented in amachine-executable program or programs, firmware, etc. The terms areused to efficiently explain content of the disclosure. Although theexamples refer to operations being performed by a particular redirectoror manager, different entities can perform different operations and belabeled with different names without substantially deviating from thedisclosure. Some of this possible variation arises from platformconstraints, system specification, programming languages, and developerdesign choices.

As will be appreciated, aspects of the disclosure may be embodied as asystem, method or program code/instructions stored in one or moremachine-readable media. Accordingly, aspects may take the form ofhardware, software (including firmware, resident software, micro-code,etc.), or a combination of software and hardware aspects that may allgenerally be referred to herein as a “circuit,” “module” or “system.”The functionality presented as individual modules/units in the exampleillustrations can be organized differently in accordance with any one ofplatform (operating system and/or hardware), application ecosystem,interfaces, programmer preferences, programming language, administratorpreferences, etc.

Any combination of one or more machine readable medium(s) may beutilized. The machine readable medium may be a machine readable signalmedium or a machine readable storage medium. A machine readable storagemedium may be, for example, but not limited to, a system, apparatus, ordevice, that employs any one of or combination of electronic, magnetic,optical, electromagnetic, infrared, or semiconductor technology to storeprogram code. More specific examples (a non-exhaustive list) of themachine readable storage medium would include the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a portable compact disc read-only memory (CD-ROM), anoptical storage device, a magnetic storage device, or any suitablecombination of the foregoing. In the context of this document, a machinereadable storage medium may be any tangible medium that can contain, orstore a program for use by or in connection with an instructionexecution system, apparatus, or device. A machine readable storagemedium is not a machine readable signal medium.

A machine readable signal medium may include a propagated data signalwith machine readable program code embodied therein, for example, inbaseband or as part of a carrier wave. Such a propagated signal may takeany of a variety of forms, including, but not limited to,electro-magnetic, optical, or any suitable combination thereof. Amachine readable signal medium may be any machine readable medium thatis not a machine readable storage medium and that can communicate,propagate, or transport a program for use by or in connection with aninstruction execution system, apparatus, or device.

Program code embodied on a machine readable medium may be transmittedusing any appropriate medium, including but not limited to wireless,wireline, optical fiber cable, RF, etc., or any suitable combination ofthe foregoing.

Computer program code for carrying out operations for aspects of thedisclosure may be written in any combination of one or more programminglanguages, including an object oriented programming language such as theJava® programming language, C++ or the like; a dynamic programminglanguage such as Python; a scripting language such as Perl programminglanguage or PowerShell script language; and conventional proceduralprogramming languages, such as the “C” programming language or similarprogramming languages. The program code may execute entirely on astand-alone machine, may execute in a distributed manner across multiplemachines, and may execute on one machine while providing results and oraccepting input on another machine.

The program code/instructions may also be stored in a machine readablemedium that can direct a machine to function in a particular manner,such that the instructions stored in the machine readable medium producean article of manufacture including instructions which implement thefunction/act specified in the flowchart and/or block diagram block orblocks.

FIG. 11 depicts an example computer system with a distributeddeduplication service module. The computer system includes a processorunit 1101 (possibly including multiple processors, multiple cores,multiple nodes, and/or implementing multi-threading, etc.). The computersystem includes memory 1107. The memory 1107 may be system memory (e.g.,one or more of cache, SRAM, DRAM, zero capacitor RAM, Twin TransistorRAM, eDRAM, EDO RAM, DDR RAM, EEPROM, NRAM, RRAM, SONOS, PRAM, etc.) orany one or more of the above already described possible realizations ofmachine-readable media. The computer system also includes a bus 1103(e.g., PCI, ISA, PCI-Express, HyperTransport® bus, InfiniBand® bus,NuBus, etc.) and a network interface 1105 (e.g., a Fiber Channelinterface, an Ethernet interface, an internet small computer systeminterface, SONET interface, wireless interface, etc.). The system alsoincludes a distributed deduplication service module 1111. Thedistributed deduplication service module 1111 performs deduplicationoperations (e.g., fingerprint generation, fingerprint comparison) inresponse to deduplication service requests for data sub-units from astorage domain. The distributed deduplication service module 1111 alsomaintains a fingerprint database and invokes operations to persist thefingerprint database into a persistent storage that is not impacted byresource management actions in a compute domain. The distributeddeduplication service module 1111 may also perform operations previouslydescribed as being performed by a garbage collector. Any one of thepreviously described functionalities may be partially (or entirely)implemented in hardware and/or on the processor unit 1101. For example,the functionality may be implemented with an application specificintegrated circuit, in logic implemented in the processor unit 1101, ina co-processor on a peripheral device or card, etc. Further,realizations may include fewer or additional components not illustratedin FIG. 11 (e.g., video cards, audio cards, additional networkinterfaces, peripheral devices, etc.). The processor unit 1101 and thenetwork interface 1105 are coupled to the bus 1103. Although illustratedas being coupled to the bus 1103, the memory 1107 may be coupled to theprocessor unit 1101.

While the aspects of the disclosure are described with reference tovarious implementations and exploitations, it will be understood thatthese aspects are illustrative and that the scope of the claims is notlimited to them. In general, techniques for providing a deduplicationservice that adapts to resource management actions and service demand asdescribed herein may be implemented with facilities consistent with anyhardware system or hardware systems. Many variations, modifications,additions, and improvements are possible.

Plural instances may be provided for components, operations orstructures described herein as a single instance. Finally, boundariesbetween various components, operations and data stores are somewhatarbitrary, and particular operations are illustrated in the context ofspecific illustrative configurations. Other allocations of functionalityare envisioned and may fall within the scope of the disclosure. Ingeneral, structures and functionality presented as separate componentsin the example configurations may be implemented as a combined structureor component. Similarly, structures and functionality presented as asingle component may be implemented as separate components. These andother variations, modifications, additions, and improvements may fallwithin the scope of the disclosure.

Use of the phrase “at least one of” preceding a list with theconjunction “and” should not be treated as an exclusive list and shouldnot be construed as a list of categories with one item from eachcategory, unless specifically stated otherwise. A clause that recites“at least one of A, B, and C” can be infringed with only one of thelisted items, multiple of the listed items, and one or more of the itemsin the list and another item not listed.

What is claimed is:
 1. A method, comprising: in response to receiving awrite request targeting a data unit, dividing the data unit intosub-units according to a sub-unit size; determining, by a redirector, anumber of deduplicator instances to instantiate based upon adeduplication service policy specifying a threshold amount of data thatcan be processed by a single deduplicator instance; creating a data unitmanifest for the data unit with an indication of an order and count ofthe sub-units; and requesting deduplication for the sub-units by thenumber of deduplicator instances based upon the data unit manifest. 2.The method of claim 1, wherein each deduplicator instance is assign upto the threshold amount of data specified by the deduplication servicepolicy.
 3. The method of claim 1, wherein determining the deduplicatorinstances to instantiate comprises: determining the deduplicatorinstances to instantiate based upon a size of the data unit.
 4. Themethod of claim 1, wherein determining the deduplicator instances toinstantiate comprises: determining the deduplicator instances toinstantiate based upon a number of sub-units into which the data unit isdivided.
 5. The method of claim 1, comprising: obtaining, from a servicedispatcher, location information for the deduplicator instances, whereinthe location information corresponds to network addresses and ports ofthe deduplicator instances.
 6. The method of claim 1, comprising:caching, by the redirector into a cache, location information retrievedfrom a service dispatcher for the deduplicator instances; and utilizingthe location information within the cache for processing a subsequentdeduplication request.
 7. The method of claim 1, comprising: contacting,off a request path associated with processing the write request, aservice dispatcher to refresh a cached used by the redirector to cachelocation information retrieved from the service dispatcher for thededuplicator instances.
 8. The method of claim 1, comprising: inresponse to determining that a deduplication service is unavailablebased upon insufficient resources in a compute domain, notifying thededuplicator instance, by a service dispatcher, that the deduplicationservice is unavailable.
 9. The method of claim 1, comprising: hosting,by a deduplication service, a garbage collector to maintain referencecount data for donor file data chunks managed within a service space inaccordance with the reference count data.
 10. The method of claim 1,comprising: scanning, by a garbage collector of the deduplicationservice, a user space within a storage backend based upon checkpoints toidentify data unit manifests added to the user space since a last scan;and incrementing reference counts for a set of sub-units indicated bythe data unit manifests.
 11. A non-transitory machine readable mediumcomprising instructions for performing a method, which when executed bya machine, causes the machine to perform operations comprising: inresponse to receiving a write request targeting a data unit, dividingthe data unit into sub-units according to a sub-unit size; determining,by a redirector, a number of deduplicator instances to instantiate basedupon a deduplication service policy specifying a threshold amount ofdata that can be processed by a single deduplicator instance; creating adata unit manifest for the data unit with an indication of an order andcount of the sub-units; and requesting deduplication for the sub-unitsby the number of deduplicator instances based upon the data unitmanifest.
 12. The non-transitory machine readable medium of claim 11,wherein each deduplicator instance is assign up to the threshold amountof data specified by the deduplication service policy.
 13. Thenon-transitory machine readable medium of claim 11, wherein determiningthe deduplicator instances to instantiate comprises: determining thededuplicator instances to instantiate based upon a size of the dataunit.
 14. The non-transitory machine readable medium of claim 11,wherein determining the deduplicator instances to instantiate comprises:determining the deduplicator instances to instantiate based upon anumber of sub-units into which the data unit is divided.
 15. Thenon-transitory machine readable medium of claim 11, comprising:obtaining, from a service dispatcher, location information for thededuplicator instances, wherein the location information corresponds tonetwork addresses and ports of the deduplicator instances.
 16. Thenon-transitory machine readable medium of claim 11, comprising: caching,by the redirector into a cache, location information retrieved from aservice dispatcher for the deduplicator instances; and utilizing thelocation information within the cache for processing a subsequentdeduplication request.
 17. The non-transitory machine readable medium ofclaim 11, comprising: contacting, off a request path associated withprocessing the write request, a service dispatcher to refresh a cachedused by the redirector to cache location information retrieved from theservice dispatcher for the deduplicator instances.
 18. A computingdevice comprising: a memory comprising machine executable code forperforming a method; and a processor coupled to the memory, theprocessor configured to execute the machine executable code to cause theprocessor to: in response to receiving a write request targeting a dataunit, divide the data unit into sub-units according to a sub-unit size;determine, by a redirector, a number of deduplicator instances toinstantiate based upon a deduplication service policy specifying athreshold amount of data that can be processed by a single deduplicatorinstance; create a data unit manifest for the data unit with anindication of an order and count of the sub-units; and requestdeduplication for the sub-units by the number of deduplicator instancesbased upon the data unit manifest.
 19. The computing device of claim 18,wherein each deduplicator instance is assign up to the threshold amountof data specified by the deduplication service policy.
 20. The computingdevice of claim 18, wherein the machine executable code causes theprocessor to: cache, by the redirector into a cache, locationinformation retrieved from a service dispatcher for the deduplicatorinstances; and utilize the location information within the cache forprocessing a subsequent deduplication request.